Oklahoma's Keilani Ricketts pitches against California in the seventh inning of an NCAA Women's College World Series tournament softball game in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. Ricketts had 16 strikeouts in the game. (AP Photo/Sue Ogrocki)

California's Jolene Henderson pitches to Oklahoma in the third inning of an NCAA Women's College World Series softball game in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. (AP Photo/Sue Ogrocki)

Oklahoma's Lauren Chamberlain, left, is forced out at home plate by California catcher Victoria Jones, right, in the third inning of an NCAA Women's College World Series softball game in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. (AP Photo/Sue Ogrocki)

Oklahoma pitcher Keilani Ricketts pitches to California in the third inning of an NCAA Women's College World Series softball game in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. (AP Photo/Sue Ogrocki)

California left fielder Jamia Reid catches a long fly ball hit by Oklahoma's Keilani Ricketts for an out in the sixth inning of an NCAA Women's College World Series softball game in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. (AP Photo/Sue Ogrocki)

Oklahoma players cheer in the dugout in the first inning of an NCAA Women's College World Series softball game against California in Oklahoma City, Friday, June 1, 2012. Oklahoma won 3-0. (AP Photo/Sue Ogrocki)

OKLAHOMA CITY — National player of the year Keilani Ricketts struck out 16 in a two-hit shutout, Georgia Casey homered and Oklahoma beat top-seeded California 3-0 on Friday night in the winners’ bracket at the Women’s College World Series

Lauren Chamberlain drove in the first two runs with a double in the third inning and a single in the fourth. Casey’s drive to straightaway center for Oklahoma’s NCAA-best 97th home run of the season made it 3-0 in the sixth inning.

Ricketts (35-7) dazzled with a sharp fastball and a biting changeup, keeping the Golden Bears (57-6) off balance throughout the night. She finished two strikeouts shy of U.S. Olympian Cat Osterman’s World Series record of 18 strikeouts in a seven-inning game in 2006.

The fourth-seeded Sooners (52-8) are off until Sunday, needing one more win to reach the finals. California will face an elimination game Saturday.

The Bears’ best scoring chance came in the sixth, when Jamia Reid started the inning by reaching on a grounder to third when Chamberlain dropped the throw at first base. The Sooners opted to walk Valerie Arioto, a national player of the year finalist, to bring the tying run to the plate. Reid stole third on the final pitch of Arioto’s walk, and Arioto swiped second moments later.

Ricketts then struck out Frani Echavarria swinging and Jace Williams looking to end the inning.

Williams had one of the Bears’ only two hits on a chopper to third with one out in the second. Victoria Jones, who put the ball in play in all three of her at-bats, singled to left with two outs in the seventh.

Ricketts struck out the side in the first, third and fourth innings and tied her season high for strikeouts.